It's a pity that the correct answer (login using DAC and set the default database and language for that login back to what they were before) isn't available.

I assumed the trigger concerned had a purpose - probably relating to corporate policy - and disabling as a quick fix would be unacceptable, also that I had followed good practise and backed up master before changing properties of a login, and since I wasn't allowed to pick the correct answer opted for what I still think is the least wrong of the options provided.